Preparation of thin SnO2 layers by inorganic sol-gel process

SnO₂ sols were prepared in the following way: (1) precipitation of metastannic acid with aqueous ammonia from aqueous solutions of SnCl₄, (2) washing the precipitates with NH₄NO₃ solution and water, (3) peptization of precipitates in water, sometimes with an addition of HNO₃, at elevated temperature using mechanical stirring. In those sols, sometimes diluted with water or ethanol, substrates (glass or silica derived wafers) were dipped and withdrawn at various rates. Gel coatings were converted into crystalline SnO₂ by thermal treatment at 600°C. Coatings with thickness between 300–2000 Å were prepared.